Chemical mechanical polishing method for tungsten

ABSTRACT

A process for chemical mechanical polishing a substrate containing tungsten is disclosed to reduce static corrosion rate and inhibit dishing of the tungsten and erosion of underlying dielectrics. The process includes providing a substrate; providing a polishing composition, containing, as initial components: water; an oxidizing agent; alginate; a dicarboxylic acid, a source of iron ions; a colloidal silica abrasive; and, optionally a pH adjusting agent; providing a chemical mechanical polishing pad, having a polishing surface; creating dynamic contact at an interface between the polishing pad and the substrate; and dispensing the polishing composition onto the polishing surface at or near the interface between the polishing pad and the substrate; wherein some of the tungsten (W) is polished away from the substrate, static corrosion rate is reduced, dishing of the tungsten (W) is inhibited as well as erosion of dielectrics underlying the tungsten (W).

FIELD OF THE INVENTION

The present invention is directed to the field of chemical mechanical polishing of tungsten to inhibit dishing of the tungsten in combination with inhibiting erosion of underlying dielectrics and to reduce static corrosion rate. More specifically, the present invention is directed to a method for chemical mechanical polishing of tungsten to inhibit dishing of the tungsten in combination with inhibiting erosion of underlying dielectrics and to reduce static corrosion rate by providing a substrate containing tungsten; providing a polishing composition, containing, as initial components: water; an oxidizing agent; alginate; a dicarboxylic acid, a source of iron ions; a colloidal silica abrasive; and, optionally a pH adjusting agent; providing a chemical mechanical polishing pad, having a polishing surface; creating dynamic contact at an interface between the polishing pad and the substrate; and dispensing the polishing composition onto the polishing surface at or near the interface between the polishing pad and the substrate where some of the tungsten is polished away from the substrate.

BACKGROUND OF THE INVENTION

In the fabrication of integrated circuits and other electronic devices, multiple layers of conducting, semiconducting and dielectric materials are deposited on or removed from a surface of a semiconductor wafer. Thin layers of conducting, semiconducting, and dielectric materials may be deposited by a number of deposition techniques. Common deposition techniques in modern processing include physical vapor deposition (PVD), also known as sputtering, chemical vapor deposition (CVD), plasma-enhanced chemical vapor deposition (PECVD), and electrochemical plating (ECP).

As layers of materials are sequentially deposited and removed, the uppermost surface of the wafer becomes non-planar. Because subsequent semiconductor processing (e.g., metallization) requires the wafer to have a flat surface, the wafer needs to be planarized. Planarization is useful in removing undesired surface topography and surface defects, such as rough surfaces, agglomerated materials, crystal lattice damage, scratches, and contaminated layers or materials.

Chemical mechanical planarization, or chemical mechanical polishing (CMP), is a common technique used to planarize substrates, such as semiconductor wafers. In conventional CMP, a wafer is mounted on a carrier assembly and positioned in contact with a polishing pad in a CMP apparatus. The carrier assembly provides a controllable pressure to the wafer, pressing it against the polishing pad. The pad is moved (e.g., rotated) relative to the wafer by an external driving force. Simultaneously therewith, a polishing composition (“slurry”) or other polishing solution is provided between the wafer and the polishing pad. Thus, the wafer surface is polished and made planar by the chemical and mechanical action of the pad surface and slurry.

Substrates in the electronics industry possess a high degree of integration where semiconductor bases include multilayers of interconnected structures. The layers and the structures include a wide variety of materials such as single crystal silicon, polycrystalline silicon, tetraethyl orthosilicate, silicon dioxide, silicon nitride, tungsten, titanium, titanium nitride and various other conductive, semiconductive and dielectric materials. Because these substrates require various processing steps, including CMP to form a final multilayered interconnected structure, it is often highly desirable to utilize polishing compositions and processes that are selective for specific materials depending on the intended applications. Unfortunately, such polishing compositions can cause excessive dishing of the conductive material which can lead to erosion of dielectric material. The topographical defects which can result from such dishing and erosion can further lead to non-uniform removal of additional materials from the substrate surface, such as barrier layer material disposed beneath the conductive material or dielectric material and produce a substrate surface having less than desirable quality which can negatively impact the performance of the integrated circuit.

Chemical mechanical polishing has become a preferred method for polishing tungsten during the formation of tungsten interconnects and contact plugs in integrated circuit designs. Tungsten is frequently used in integrated circuit designs for contact/via plugs. Typically, a contact or via hole is formed through a dielectric layer on a substrate to expose regions of an underlying component, for example, a first level metallization or interconnect. Unfortunately, many CMP slurries used to polish tungsten cause the problem of dishing. The severity of the dishing can vary but it typically is severe enough to cause erosion of underlying dielectric materials such as TEOS.

Another problem associated with polishing metals such as tungsten is corrosion. The corrosion of metals is a common side-effect of CMP. During the CMP process the metal polishing slurry that remains on the surface of the substrate continues to corrode the substrate beyond the effects of the CMP. Sometimes corrosion is desired; however, in most semiconductor processes corrosion is to be reduced or inhibited. Corrosion may also contribute to surface defects such as pitting and key-holing. These surface defects significantly affect the final properties of the semiconductor device and hamper its usefulness. Therefore, there is a need for a CMP polishing method and composition for tungsten which inhibits dishing of tungsten and erosion of underlying dielectric materials such as TEOS and also reduces static corrosion rate.

SUMMARY OF THE INVENTION

The present invention provides a method of chemical mechanical polishing tungsten, comprising: providing a substrate comprising tungsten and a dielectric; providing a chemical mechanical polishing composition, comprising, as initial components: water; an oxidizing agent; alginate; a colloidal silica abrasive; a dicarboxylic acid or salt thereof; a source of iron (III) ions; and, optionally, a pH adjusting agent; providing a chemical mechanical polishing pad, having a polishing surface; creating dynamic contact at an interface between the chemical mechanical polishing pad and the substrate; and dispensing the chemical mechanical polishing composition onto the polishing surface of the chemical mechanical polishing pad at or near the interface between the chemical mechanical polishing pad and the substrate; wherein some of the tungsten is polished away from the substrate.

The present invention provides a chemical mechanical method of polishing tungsten, comprising: providing the substrate comprising tungsten and a dielectric; providing a chemical mechanical polishing composition, comprising, as initial components: water; an oxidizing agent; alginate; a colloidal silica abrasive having a negative zeta potential; a dicarboxylic acid or salt thereof; a source of iron (III) ions; and, optionally, a pH adjusting agent; providing a chemical mechanical polishing pad, having a polishing surface; creating dynamic contact at an interface between the chemical mechanical polishing pad and the substrate; and dispensing the chemical mechanical polishing composition onto the polishing surface of the chemical mechanical polishing pad at or near the interface between the chemical mechanical polishing pad and the substrate; wherein some of the tungsten is polished away from the substrate; wherein the chemical mechanical polishing composition provided has a tungsten removal rate of ≥1,000 Å/min with a platen speed of 80 revolutions per minute, a carrier speed of 81 revolutions per minute, a chemical mechanical polishing composition flow rate of 125 mL/min, a nominal down force of 21.4 kPa on a 200 mm polishing machine; and, wherein the chemical mechanical polishing pad comprises a polyurethane polishing layer containing polymeric hollow core microparticles and a polyurethane impregnated non-woven subpad.

The present invention provides a chemical mechanical method of polishing tungsten, comprising: providing a substrate comprising tungsten and a dielectric; providing a chemical mechanical polishing composition, comprising, as initial components: water; an oxidizing agent; alginate in an amount of at least 50 ppm; a colloidal silica abrasive having a negative zeta potential; malonic acid or salt thereof; a source of iron (III) ions; and, optionally, a pH adjusting agent; providing a chemical mechanical polishing pad, having a polishing surface; creating dynamic contact at an interface between the chemical mechanical polishing pad and the substrate; and dispensing the chemical mechanical polishing composition onto the polishing surface of the chemical mechanical polishing pad at or near the interface between the chemical mechanical polishing pad and the substrate; wherein some of the tungsten is polished away from the substrate; wherein the chemical mechanical polishing composition provided has a tungsten removal rate of ≥1,000 Å/min with a platen speed of 80 revolutions per minute, a carrier speed of 81 revolutions per minute, a chemical mechanical polishing composition flow rate of 125 mL/min, a nominal down force of 21.4 kPa on a 200 mm polishing machine; wherein the chemical mechanical polishing pad comprises a polyurethane polishing layer containing polymeric hollow core microparticles and a polyurethane impregnated non-woven subpad.

The present invention provides a method of chemical mechanical polishing tungsten, comprising: providing the substrate comprising tungsten and a dielectric; providing a chemical mechanical polishing composition, comprising, as initial components: water; 0.01 to 10 wt % of an oxidizing agent, wherein the oxidizing agent is hydrogen peroxide; 50 ppm to 1000 ppm of alginate; 0.01 to 10 wt % of a colloidal silica abrasive having a negative zeta potential; 100 to 1,400 ppm malonic acid or salt thereof; 100 to 1,000 ppm of a source of iron (III) ions, wherein the source of iron (III) ions is ferric nitrate nonahydrate; and, optionally, a pH adjusting agent; wherein the chemical mechanical polishing composition has a pH of 1 to 7; providing a chemical mechanical polishing pad, having a polishing surface; creating dynamic contact at an interface between the chemical mechanical polishing pad and the substrate; and dispensing the chemical mechanical polishing composition onto the polishing surface of the chemical mechanical polishing pad at or near the interface between the chemical mechanical polishing pad and the substrate; wherein some of the tungsten is polished away from the substrate.

The present invention provides a method of chemical mechanical polishing tungsten, comprising: providing a substrate comprising tungsten and a dielectric; providing a chemical mechanical polishing composition, comprising, as initial components: water; 1 to 3 wt % of an oxidizing agent, wherein the oxidizing agent is hydrogen peroxide; 600 to 900 ppm alginate, 0.2 to 2 wt % of a colloidal silica abrasive having a negative surface charge; 120 to 1,350 ppm of malonic acid; 250 to 400 ppm of a source of iron (III) ions, wherein the source of iron (III) ions is ferric nitrate nonahydrate; and, optionally, a pH adjusting agent; wherein the chemical mechanical polishing composition has a pH of 2 to 2.5; providing a chemical mechanical polishing pad, having a polishing surface; creating dynamic contact at an interface between the chemical mechanical polishing pad and the substrate; and dispensing the chemical mechanical polishing composition onto the polishing surface of the chemical mechanical polishing pad at or near the interface between the chemical mechanical polishing pad and the substrate; wherein some of the tungsten is polished away from the substrate.

The foregoing methods of the present invention use a chemical mechanical polishing composition comprising alginate which polishes tungsten and inhibits dishing of the tungsten in combination with inhibiting erosion of underlying dielectrics. The method also reduces static corrosion rate.

DETAILED DESCRIPTION OF THE INVENTION

As used throughout this specification the following abbreviations have the following meanings, unless the context indicates otherwise: ° C.=degrees Centigrade; g=grams; L=liters; mL=milliliters; μ=μm=microns; kPa=kilopascal; Å=angstroms; mV=millivolts; DI=deionized; ppm=parts per million=mg/L; mm=millimeters; cm=centimeter; min=minute; rpm=revolutions per minute; lbs=pounds; kg=kilograms; W=tungsten; PO=propylene oxide; EO=ethylene oxide; ICP-OES=inductively coupled plasma optical emission spectroscopy; wt %=percent by weight; and RR=removal rate.

The term “chemical mechanical polishing” or “CMP” refers to a process where a substrate is polished by means of chemical and mechanical forces alone and is distinguished from electrochemical-mechanical polishing (ECMP) where an electric bias is applied to the substrate. The term “alginate” includes alginic acid and its anionic polysaccharide species with counter positively charged species. The term “starch” means a polysaccharide composed of a large number of glucose units joined by glycosidic bonds. The term “TEOS” means the silicon dioxide formed from the decomposition of tetraethyl orthosilicate (Si(OC2H5)4). The terms “a” and “an” refer to both the singular and the plural. All percentages are by weight, unless otherwise noted. All numerical ranges are inclusive and combinable in any order, except where it is logical that such numerical ranges are constrained to add up to 100%.

The method of polishing a substrate of the present invention uses a chemical mechanical polishing composition containing an oxidizing agent; alginate; a colloidal silica abrasive; a dicarboxylic acid or salt thereof; a source of iron (III) ions; and, optionally, a pH adjusting agent to provide for the removal of tungsten from the substrate surface while inhibiting dishing of the tungsten, erosion of underlying dielectric materials and reducing static corrosion rate.

Preferably, the method of polishing a substrate of the present invention, comprises: providing the substrate, wherein the substrate comprises tungsten and a dielectric; providing a chemical mechanical polishing composition, comprising, preferably, consisting of, as initial components: water; an oxidizing agent, preferably in amounts of at least 0.01 wt % to 10 wt %, more preferably in amounts of 0.1 wt % to 5 wt %, still more preferably from 1 wt % to 3 wt %; alginate in amounts of, preferably, at least 50 ppm, more preferably 50 ppm to 1000 ppm, even more preferably from 600 ppm to 1000 ppm, still more preferably from 600 ppm to 900 ppm; a colloidal silica abrasive, preferably in amounts of 0.01 wt % to 10 wt %, more preferably from 0.05 wt % to 7.5 wt %, even more preferably from 0.1 wt % to 5 wt %, still more preferably from 0.2 wt % to 2 wt %; a dicarboxylic acid, salt thereof or mixtures thereof, preferably in amounts of 100 ppm to 1400 ppm, more preferably from 120 ppm to 1350 ppm; a source of iron (III) ions, preferably, wherein the source of iron (III) ions is ferric nitrate nonahydrate; and, optionally, a pH adjusting agent; preferably, wherein the chemical mechanical polishing composition has a pH of 1 to 7; more preferably, of 1.5 to 4.5; still more preferably, 1.5 to 3.5; most preferably, of 2 to 2.5; providing a chemical mechanical polishing pad, having a polishing surface; creating dynamic contact at an interface between the chemical mechanical polishing pad and the substrate; and dispensing the chemical mechanical polishing composition onto the polishing surface of the chemical mechanical polishing pad at or near the interface between the chemical mechanical polishing pad and the substrate; wherein at least some of the tungsten is polished away from the substrate.

Preferably, in the method of polishing a substrate of the present invention, the substrate comprises tungsten and a dielectric. More preferably, the substrate provided is a semiconductor substrate comprising tungsten and a dielectric. Most preferably, the substrate provided is a semiconductor substrate comprising tungsten deposited within at least one of holes and trenches formed in a dielectric such as TEOS.

Preferably, in the method of polishing a substrate of the present invention, the water contained, as an initial component, in the chemical mechanical polishing composition provided is at least one of deionized and distilled to limit incidental impurities.

Preferably, in the method of polishing a substrate of the present invention, the chemical mechanical polishing composition provided contains, as an initial component, an oxidizing agent, wherein the oxidizing agent is selected from the group consisting of hydrogen peroxide (H₂O₂), monopersulfates, iodates, magnesium perphthalate, peracetic acid and other per-acids, persulfate, bromates, perbromate, persulfate, peracetic acid, periodate, nitrates, iron salts, cerium salts, Mn (III), Mn (IV) and Mn (VI) salts, silver salts, copper salts, chromium salts, cobalt salts, halogens, hypochlorites and a mixture thereof. More preferably, the oxidizing agent is selected from hydrogen peroxide, perchlorate, perbromate; periodate, persulfate and peracetic acid. Most preferably, the oxidizing agent is hydrogen peroxide.

Preferably, in the method of polishing a substrate of the present invention, the chemical mechanical polishing composition provided contains, as an initial component, 0.01 to 10 wt %, more preferably, 0.1 to 5 wt %; most preferably, 1 to 3 wt % of an oxidizing agent.

Preferably, in the method of polishing a substrate of the present invention, the chemical mechanical polishing composition provided contains, as an initial component, a source of iron (III) ions. More preferably, in the method of the present invention, the chemical mechanical polishing composition provided contains, as an initial component, a source of iron (III) ions, wherein the source of iron (III) ions is selected from the group consisting iron (III) salts. Most preferably, in the method of the present invention, the chemical mechanical polishing composition provided contains, as an initial component, a source of iron (III) ions, wherein the source of iron (III) ions is ferric nitrate nonahydrate, (Fe(NO₃)₃.9H₂O).

Preferably, in the method of polishing a substrate of the present invention, the chemical mechanical polishing composition provided contains, as an initial component, a source of iron (III) ions sufficient to introduce 1 to 200 ppm, preferably, 5 to 150 ppm, more preferably, 7.5 to 125 ppm, most preferably, 10 to 100 ppm of iron (III) ions to the chemical mechanical polishing composition.

Preferably, in the method of polishing a substrate of the present invention, the chemical mechanical polishing composition provided contains, as an initial component, a source of iron (III) ions. More preferably, in the method of polishing a substrate of the present invention, the chemical mechanical polishing composition provided contains, as an initial component, 100 to 1,000 ppm, preferably, 150 to 750 ppm, more preferably, 200 to 500 ppm and most preferably, 250 to 400 ppm of a source of iron (III) ions. Most preferably, in the method of polishing a substrate of the present invention, the chemical mechanical polishing composition provided contains, as an initial component, 100 to 1,000 ppm, preferably, 150 to 750 ppm, more preferably, 200 to 500 ppm, most preferably, 250 to 400 ppm of a source of iron (III) ions, wherein the source of iron (III) ions is ferric nitrate nonahydrate, (Fe(NO₃)₃.9H₂O).

Preferably, in the method of polishing a substrate of the present invention, the chemical mechanical polishing composition provided contains, as an initial component, alginate, wherein alginate includes one or more of alginic acid and its anionic species, wherein an anionic species of alginate further includes one or more positively charged counter ion species selected from the group consisting of alkali metal cations, cesium cations, magnesium cations, calcium cations, barium cations, aluminum cations, transition metal cations, and organic positively charged species. Preferably, the anionic species further includes one or more counter cations selected from the group consisting of alkali metal cations, magnesium cations, calcium cations, barium cations and aluminum cations. More preferably the one or more cation species is selected from the group consisting of alkali metal cations, magnesium cations, calcium cations and barium cations. Still more preferably the one or more cation species are selected from the group consisting of alkali metal cations, wherein it is preferred that the alkali metal cation species is sodium or potassium, more preferably the alkali metal cation species is sodium, wherein it is most preferred that the alginate species is alginic acid sodium salt from brown algae. Preferably the positively charged organic species is propylene glycol. Preferably, in the method of polishing a substrate of the present invention, the chemical mechanical polishing composition provided contains, as an initial component, at least 50 ppm, more preferably 50 ppm to 1000 ppm, even more preferably from 600 ppm to 1000 ppm, still more preferably from 600 ppm to 900 ppm of alginate.

Preferably, in the method of polishing a substrate of the present invention, the chemical mechanical polishing composition provided contains a colloidal silica abrasive having a negative zeta potential. More preferably, in the method of polishing a substrate of the present invention, the chemical mechanical polishing composition provided contains a colloidal silica abrasive having a permanent negative zeta potential, wherein the chemical mechanical polishing composition has a pH of 1 to 7, preferably, of 1.5 to 4.5; more preferably, of 1.5 to 3.5; still more preferably, of 2 to 2.5. Still more preferably, in the method of polishing a substrate of the present invention, the chemical mechanical polishing composition provided contains a colloidal silica abrasive having a permanent negative zeta potential, wherein the chemical mechanical polishing composition has a pH of 1 to 7, preferably, of 1.5 to 4.5; more preferably, of 1.5 to 3.5; still more preferably, of 2 to 2.5 as indicated by a zeta potential from −0.1 mV to −20 mV.

Preferably, in the method of polishing a substrate of the present invention, the chemical mechanical polishing composition provided contains, as an initial component, a colloidal silica abrasive, wherein the colloidal silica abrasive has an average particle size ≤100 nm, preferably, 5 to 100 nm; more preferably, 10 to 60 nm; most preferably, 20 to 60 nm as measured by dynamic light scattering techniques.

Preferably, in the method of polishing a substrate of the present invention, the chemical mechanical polishing composition provided contains 0.01 to 10 wt %, preferably 0.05 to 7.5 wt %, more preferably, 0.1 to 5 wt %, most preferably, 0.2 to 2 wt % of a colloidal silica abrasive. Preferably the colloidal silica abrasive has a negative zeta potential.

Preferably, in the method of polishing a substrate of the present invention, the chemical mechanical polishing composition provided contains, as an initial component, a dicarboxylic acid, wherein the dicarboxylic acid includes, but is not limited to malonic acid, oxalic acid, succinic acid, adipic acid, maleic acid, malic acid, glutaric acid, tartaric acid, salts thereof or mixtures thereof. More preferably, in the method of polishing a substrate of the present invention, the chemical mechanical polishing composition provided contains, as an initial component, a dicarboxylic acid, wherein the dicarboxylic acid is selected from the group consisting of malonic acid, oxalic acid, succinic acid, tartaric acid, salts thereof and mixtures thereof. Still more preferably the chemical mechanical polishing composition provided contains, as an initial component, a dicarboxylic acid, wherein the dicarboxylic acid is selected from the group consisting of malonic acid, oxalic acid, succinic acid, salts thereof and mixtures thereof. Most preferably in the method of polishing a substrate of the present invention, the chemical mechanical polishing composition provided contains, as an initial component, the dicarboxylic acid malonic acid or salts thereof.

Preferably, in the method of polishing a substrate of the present invention, the chemical mechanical polishing composition provided contains, as an initial component, 1 to 2,600 ppm, preferably, 100 to 1,400 ppm, more preferably, 120 to 1,350 ppm, still more preferably, 130 to 1,100 ppm, of a dicarboxylic acid, wherein the dicarboxylic acid includes, but is not limited to malonic acid, oxalic acid, succinic acid, adipic acid, maleic acid, malic acid, glutaric acid, tartaric acid, salts thereof or mixtures thereof. More preferably, in the method of polishing a substrate of the present invention, the chemical mechanical polishing composition provided contains, as an initial component, 1 to 2,600 ppm of malonic acid or salts thereof. Most preferably, in the method of polishing a substrate of the present invention, the chemical mechanical polishing composition provided contains, as an initial component 100 to 1,400 ppm, more preferably, 120 to 1,350 ppm, still more preferably, 130 to 1,350 ppm, the dicarboxylic acid malonic acid or salts thereof.

Preferably, in the method of polishing a substrate of the present invention, the chemical mechanical polishing composition provided has a pH of 1 to 7. More preferably, in the method of polishing a substrate of the present invention, the chemical mechanical polishing composition provided has a pH of 1.5 to 4.5. Still more preferably, in the method of polishing a substrate of the present invention, the chemical mechanical polishing composition provided has a pH of 1.5 to 3.5. Most preferably, in the method of polishing a substrate of the present invention, the chemical mechanical polishing composition provided has a pH of 2 to 2.5.

Preferably, in the method of polishing a substrate of the present invention, the chemical mechanical polishing composition provided optionally contains a pH adjusting agent. Preferably, the pH adjusting agent is selected from the group consisting of inorganic and organic pH adjusting agents. Preferably, the pH adjusting agent is selected from the group consisting of inorganic acids and inorganic bases. More preferably, the pH adjusting agent is selected from the group consisting of nitric acid and potassium hydroxide. Most preferably, the pH adjusting agent is potassium hydroxide.

Preferably, in the method of polishing a substrate of the present invention, the chemical mechanical polishing pad provided can by any suitable polishing pad known in the art. One of ordinary skill in the art knows to select an appropriate chemical mechanical polishing pad for use in the method of the present invention. More preferably, in the method of polishing a substrate of the present invention, the chemical mechanical polishing pad provided is selected from woven and non-woven polishing pads. Still more preferably, in the method of polishing a substrate of the present invention, the chemical mechanical polishing pad provided comprises a polyurethane polishing layer. Most preferably, in the method of polishing a substrate of the present invention, the chemical mechanical polishing pad provided comprises a polyurethane polishing layer containing polymeric hollow core microparticles and a polyurethane impregnated non-woven subpad. Preferably, the chemical mechanical polishing pad provided has at least one groove on the polishing surface.

Preferably, in the method of polishing a substrate of the present invention, the chemical mechanical polishing composition provided is dispensed onto a polishing surface of the chemical mechanical polishing pad provided at or near an interface between the chemical mechanical polishing pad and the substrate.

Preferably, in the method of polishing a substrate of the present invention, dynamic contact is created at the interface between the chemical mechanical polishing pad provided and the substrate with a down force of 0.69 to 34.5 kPa normal to a surface of the substrate being polished.

Preferably, in the method of polishing a substrate of the present invention, wherein the chemical mechanical polishing composition provided has a tungsten removal rate ≥1,000 Å/min; preferably, ≥1,500 Å/min; more preferably, ≥2,000 Å/min. More preferably, in the method of polishing a substrate of the present invention, wherein the chemical mechanical polishing composition provided has a tungsten removal rate of ≥1,000 Å/min; preferably, ≥1,500 Å/min; more preferably, ≥2,000 Å/min; and a W/TEOS selectivity of ≥5. Still more preferably, in the method of polishing a substrate of the present invention, wherein the tungsten is removed from the substrate at a removal rate of ≥1,000 Å/min; preferably, ≥1,500 Å/min; more preferably, ≥2,000 Å/min; and a W/TEOS selectivity of 5 to 15. Most preferably, in the method of polishing the substrate of the present invention, wherein the tungsten is removed from the substrate at a removal rate of ≥1,000 Å/min; preferably, ≥1,500 Å/min; more preferably, ≥2,000 Å/min; and a W/TEOS selectivity and with a platen speed of 80 revolutions per minute, a carrier speed of 81 revolutions per minute, a chemical mechanical polishing composition flow rate of 125 mL/min, a nominal down force of 21.4 kPa on a 200 mm polishing machine; and, wherein the chemical mechanical polishing pad comprises a polyurethane polishing layer containing polymeric hollow core microparticles and a polyurethane impregnated non-woven subpad.

As is illustrated in the following Examples the alginate CMP methods of the present invention inhibit tungsten dishing in combination with inhibiting erosion of underlying TEOS and further inhibit static corrosion rate.

EXAMPLE 1 Slurry Formulations

The chemical mechanical polishing compositions of this Example were prepared by combining the components in the amounts listed in Table 1 with the balance being DI water and adjusting the pH of the compositions to the final pH listed in Table 1 with 45 wt % potassium hydroxide.

TABLE 1 Malonic Abrasive¹ Polysaccharide Fe(NO₃)₃ Acid H₂O₂ Slurry # (wt %) (ppm) (ppm) (ppm) (wt %) pH CS-1 2 — 362 1320 2 2.3 PS-1 2 Starch (150) 362 1320 2 2.3 PS-2 2 Alginate² (750) 362 1320 2 2.3 ¹KLEBOSOL ™ 1598-B25 (—) zeta potential abrasive slurry manufactured by AZ Electronics Materials, available from The Dow Chemical Company; and ²Available from Sigma-Aldrich (alginic acid sodium salt from brown algae, low viscosity, CAS9005-38-3)

EXAMPLE 2 Static Corrosion Rate Performance of Polysaccharide CMP Slurries

The static corrosion tests were carried out by immersing W blanket wafers (1 cm×4 cm) in 15 g slurry samples. The W wafers were removed from tested slurries after 10 min. The solutions were subsequently centrifuged for 20 min at 9,000 rpm to remove slurry particles. The supernatant was analyzed by ICP-OES to determine the amount of tungsten by weight. The static corrosion rate (Å/min) was converted from the W mass assuming an etching wafer surface area of 4 cm². The results of the static corrosion tests are in Table 2.

TABLE 2 Slurry # W Static Corrosion Rate (Å/min) CS-1 29 PS-1 25 PS-2 21

The results of the static corrosion rate tests showed that the chemical mechanical polishing slurries containing alginate effectively reduced the static corrosion on W containing wafers better than the control slurry (CS-1) as well as to the slurry (PS-1) which included the polysaccharide starch.

EXAMPLE 3 Chemical Mechanical Polishing—Dishing and Erosion Performance of Alginate CMP Slurry

The polishing experiments were performed on 200 mm blanket wafers installed on an Applied Materials 200 mm MIRRA® polishing machine. The polishing removal rate experiments were performed on 200 mm blanket 15 kÅ-thick TEOS sheet wafers plus W, Ti, and TiN blanket wafers available from Silicon Valley Microelectronics. All polishing experiments were performed using an IC1010™ polyurethane polishing pad paired with an SP2310 subpad commercially available from Rohm and Haas Electronic Materials CMP Inc.) with a typical down pressure of 21.4 kPa (3.1 psi), a chemical mechanical polishing composition flow rate of 125 mL/min, a table rotation speed of 80 rpm and a carrier rotation speed of 81 rpm unless specified otherwise. A Kinik PDA33A-3 diamond pad conditioner (commercially available from Kinik Company) was used to dress the polishing pad. The polishing pad was broken in with the conditioner using a down force of 9.0 lbs (4.1 kg) for 15 minutes and 7.0 lbs (3.2 kg) for 15 minutes at 80 rpm (platen)/36 rpm (conditioner). The polishing pad was further conditioned ex-situ prior to polishing using a down force of 7 lbs (3.2 kg) for 24 seconds. The TEOS erosion depths were determined by measuring the film thickness before and after polishing using a KLA-Tencor FX200 metrology tool. The W removal and dishing rates were determined using a KLA-Tencor RS100C metrology tool. The wafers had varying standard line width features as shown in Tables 3A and 3B. In the tables of this example the numerator refers to W and the denominator refers to TEOS.

3A 100/100 μm 100/100 μm 50/50 μm 50/50 μm dishing erosion 10/10 μm 10/10 μm Slurry # dishing (Å) erosion (Å) (Å) (Å) dishing (Å) erosion (Å) PS-1 1180 57 1337 17 604 236 PS-2 941 52 1051 22 502 187

3B 0.25/0.25 μm 0.25/0.25 μm 7/3 μm 7/3 μm 9/1 μm 9/1 μm dishing erosion Slurry # dishing (Å) erosion (Å) dishing (Å) erosion (Å) (Å) (Å) PS-1 383 610 336 1103 132 336 PS-2 320 567 272 906 142 226

Overall the slurry which included alginate showed improved performance over the slurry which included starch. The alginate slurry showed overall reduced dishing of W and reduced erosion of TEOS.

EXAMPLE 4 W, TEOS Removal Rate and W, TEOS Maximum Polishing Temperature

The polishing experiments for W and TEOS removal rates were performed substantially as described in Example 3 using the same apparatus and parameters. The wafers were from Silicon Valley Microelectronics. The results are in Table 4.

TABLE 4 W RR TEOS RR W/TEOS W Temp. TEOS Temp. Slurry # (Å/min) (Å/min) Selectivity (° C.) (° C.) PS-1 1881 180 10 35 33.7 PS-2 1583 271 6 33.6 30.8

Although the W/TEOS selectivity of the alginate slurry was not as high as for starch slurry, the alginate chemical mechanical polishing composition of the present invention still showed good W RR of greater than 1000 Å/min and good W/TEOS selectivity. 

What is claimed is:
 1. A method of chemical mechanical polishing tungsten, comprising: providing a substrate comprising tungsten and a dielectric; providing a chemical mechanical polishing composition, comprising, as initial components: water; an oxidizing agent; alginate; a colloidal silica abrasive; a dicarboxylic acid, a source of iron (III) ions; and, optionally, a pH adjusting agent; providing a chemical mechanical polishing pad, having a polishing surface; creating dynamic contact at an interface between the chemical mechanical polishing pad and the substrate; and dispensing the chemical mechanical polishing composition onto the polishing surface of the chemical mechanical polishing pad at or near the interface between the chemical mechanical polishing pad and the substrate to remove at least some of the tungsten.
 2. The method of claim 1, wherein the chemical mechanical polishing composition provided has a tungsten removal rate of ≥1,000 Å/min with a platen speed of 80 revolutions per minute, a carrier speed of 81 revolutions per minute, a chemical mechanical polishing composition flow rate of 125 mL/min, a nominal down force of 21.4 kPa on a 200 mm polishing machine; and, wherein the chemical mechanical polishing pad comprises a polyurethane polishing layer containing polymeric hollow core microparticles and a polyurethane impregnated non-woven subpad.
 3. The method of claim 1, wherein the chemical mechanical polishing composition, provided comprises, as initial components: the water; 0.01 to 10 wt % of the oxidizing agent, wherein the oxidizing agent is hydrogen peroxide; 50 to 1000 ppm of the alginate; 0.01 to 10 wt % of the colloidal silica abrasive; 1 to 2,600 ppm of the dicarboxylic acid; 100 to 1,000 ppm of the source of iron (III) ions, wherein the source of iron (III) ions is ferric nitrate nonahydrate; and, optionally, the pH adjusting agent; wherein the chemical mechanical polishing composition has a pH of 1 to
 7. 4. The method of claim 3, wherein the chemical mechanical polishing composition provided has a tungsten removal rate of ≥1,000 Å/min with a platen speed of 80 revolutions per minute, a carrier speed of 81 revolutions per minute, a chemical mechanical polishing composition flow rate of 125 mL/min, a nominal down force of 21.4 kPa on a 200 mm polishing machine; and, wherein the chemical mechanical polishing pad comprises a polyurethane polishing layer containing polymeric hollow core microparticles and a polyurethane impregnated non-woven subpad.
 5. The method of claim 1, wherein the chemical mechanical polishing composition, provided comprises, as initial components: the water; 0.1 to 5 wt % of the oxidizing agent, wherein the oxidizing agent is hydrogen peroxide; 600 to 1000 ppm of the alginate; 0.05 to 7.5 wt % of the colloidal silica abrasive; 100 to 1,400 ppm of the dicarboxylic acid; 150 to 750 ppm of the source of iron (III) ions, wherein the source of iron (III) ions is ferric nitrate; and, optionally, the pH adjusting agent; wherein the chemical mechanical polishing composition has a pH of 1.5 to 4.5.
 6. The method of claim 5, wherein the chemical mechanical polishing composition provided has a tungsten removal rate of ≥1,000 Å/min with a platen speed of 80 revolutions per minute, a carrier speed of 81 revolutions per minute, a chemical mechanical polishing composition flow rate of 125 mL/min, a nominal down force of 21.4 kPa on a 200 mm polishing machine; and, wherein the chemical mechanical polishing pad comprises a polyurethane polishing layer containing polymeric hollow core microparticles and a polyurethane impregnated non-woven subpad.
 7. The method of claim 1, wherein the chemical mechanical polishing composition, provided comprises, as initial components: the water; 0.1 to 3 wt % of the oxidizing agent, wherein the oxidizing agent is hydrogen peroxide; 600 to 900 ppm of the alginate; 0.1 to 5 wt % of the colloidal silica abrasive; 120 to 1,350 ppm of the dicarboxylic acid, wherein the dicarboxylic acid is malonic acid; 200 to 500 ppm of the source of iron (III) ions, wherein the source of iron (III) ions is ferric nitrate; and, optionally, the pH adjusting agent; wherein the chemical mechanical polishing composition has a pH of 1.5 to 3.5.
 8. The method of claim 7, wherein the chemical mechanical polishing composition provided has a tungsten removal rate of ≥1,000 Å/min with a platen speed of 80 revolutions per minute, a carrier speed of 81 revolutions per minute, a chemical mechanical polishing composition flow rate of 125 mL/min, a nominal down force of 21.4 kPa on a 200 mm polishing machine; and, wherein the chemical mechanical polishing pad comprises a polyurethane polishing layer containing polymeric hollow core microparticles and a polyurethane impregnated non-woven subpad. 